Exhaust jet cooling pump for internal combustion engine



EXHAUST JET COOLING PUMP FOR INTERNAL COMBUSTION ENGINE Filed Sept. 23. 1955 March 6, 1956 J. w. THORP EIAL 4 Sheets-Sheet 1 INVENTORS. don/v WILLARD THORP RQLP-H Howneo Swmsaooo LlnMss HnLL RYDEE EXHAUST JET COOLING PUMP FOR INTERNAL COMBUSTION ENGINE Filed Sept. 23, 1953 March 6, 1956 J. w. THORP ETAL 4 Sheets-Sheet 2 INVENTORS JOHN WILLARD THORP RALPH Howmw Swmsaooo- James Hnu. RYDER BY THE/R flmlA/EXf MAW/s, Mac/ F65 r5? J hive/5 March 6, 1956 w, THORP ETAL 2,737,164

EXHAUST JET COOLING PUMP FOR INTERNAL COMBUSTION ENGINE Filed Sept. 23, 1953 4 Sheets-Sheet 3 Egg 46 M 48 INVENTORS.

JOHN W/LLQRD THORP RALPH Ho WARD SWH/SGOOD 4 L/HMES HALL RYDER BY THEIR 4 70160575 March 6, 1956 w, THORP ETAL 2,737,164

EXHAUST JET COOLING PUMP FOR INTERNAL COMBUSTION ENGINE Filed Sept. 23. 1953 4 Sheets-Sheet 4 Coo/I09 Gas /NVNTOR$. vJOHN WILLARD THORP RnLPH Howr-mo Swmsaooo Ja/vms HHLL RYDER B Y THfi/l? A MIA Er: f/Amsms, 406m; fEsreR 40%Rms United States Patent signors to Fletcher Aviation, Corporation, Pasadena, Calif., a corporation of California Application September 23, 1953, Serial No. 381,889 4 Claims. ((11. 12341.64)

The present invention relates to a new and improved typeof exhaust jet cooling pump utilized in internal coinbustion engines.

, It has been known for many years that it would be theoretically possible to cool various air-cooled engines by an air stream created by 'virtue of the velocity of the exhaust from the engine proper. A number of prior attempts to effect such cooling have been shown in the patent literature on the subject. 7 Among these attempts is the patent to Rea, No. 657,451, illustrating a cylinder for an engine in which there is an air inlet leading around the fins of the cylinder to a very simply constructed exhau'st venturi near the head of the cylinder. Unfortunately, the patentee in this case failed to realize that to obtain effective cooling action by means of the air streamdrawn by this exhaust jet, a very careful control of the flow around the cylinder port proper was necessary. Subsequent attempts at such control, such as are illustrated by the Bowen Patent 1,424,234, failed because they relied for their eflectiveness upon a plurality of ports placed within a vent head or chamber positioned over a single part of the motor being cooled. By virtue of the location of these ports there was a concentration of the air from the furthest port from the discharge tube toward this discharge tube, resulting in ineffective unequal cooling throughout the area involved. The device illustrated by the patent, as nearly as can be told, has never come into commercial use because of its impracticability.

More recent attempts at utilizing the exhaust stream to cool an air-cooled engine are shown by the Koppen Patent 2,410,856. Here there are illustrated a plurality of exhaust jets discharging into a central mufiler bafiletype structure. These jets are arranged in such a manner that the air from around all of the air-cooled cylinders is mixed prior to its entrance into the exhaust stream proper. No efiective control is provided for these various air streams and, in effect, the cooling of various parts of the engine is haphazard inasmuch as there is no such control. In order for an air-cooled internal combustion engine to operate properly, all parts thereof must be satisfactorily cooled to a predetermined extent.

It is an object of the instant invention to overcome the foregoing and related defects of the prior art showing engines cooled by an air stream created by means of a jet attached to the exhaust of the engine. A further object of the invention is to produce a new and improved type of cooling means for air-cooled engines. A still further object is to produce a cooling means for air-cooled engines which is simple, effective and relatively cheap to manufacture.

Other objects of the invention, as well as the advantages of it, will be apparent from the aceompanying specification, including the appended claims as well as the accompanying drawings, in which:

Fig. 1 shows a side view of an engine cooled in accordance with the invention;

Fig. 2 shows an end view of the device illustrated in Fig. 1;

Fig. "3 illustrates a sectional view taken at line s s of Fig. 2; v I Fig. 4 illustrates a sectional view taken at line 4-4 of Fig. 2;

Fig. 5 illustrates a sectional view taken at line 55 of Fig. 2; p I Fig. 6 shows a sectional view taken at line 66 of Fig. 1; p Fig. 7 shows a sectional view taken at line 77 of Fig. 2;

Fig. 8 is an isometric view of a cooling section of the type used on an engine as illustrated in Fig. 1;

Fig. 9 shows a view similar to Fig. 7, illustrating a modified construction; and V Figs. 10 and 11 are diagrammatic views of modified cooling constructions of the invention.

Briefly, the above and related aims are accomplished by creating a cooling system for an air-cooled internal combustion engine in which a plurality of cooling air streams discharge together in the vicinity of an exhaust gas jet, and in which these air streams are pulled by a vacuum created by this exhaust gas. Each of these streams of air as used is employed to cool a different part of the internal combustion engine so as to obtain optimum engine cooling characteristics. The quantities of exhaust gas and air used, as well as their velocities and temperatures, are all critical with the invention.

Perhaps the invention is best described with reference to the accompanying drawings. An engine 10 is shown generally as being cooled by the meansherein described. Only sufiicient of this engine to illustrate the cooling means employed is shown. It is to be understood that the present invention is, at the present time, considered to be primarily useful with air-cooled internal combustion engines employing horizontally opposed cylinders, although it is not by any means restrictcdthereto.

This invention is applicable to internal combustion engines of any number and any disposition of cylinders. The engine illustrated is shown as having two cylinder walls 11 surrounded by cylindrical fins 12, the fins of both cylinders being partially surrounded by cylindrical fin baffies 43 terminating at the top thereof in plenum boxes 44 having a common center plenum wall 45. At the bottom of the cylinder fins 12 there is positioned a triangular divider 46 splitting the space leading between the two cylinders illustrated in the drawing into two separate sections or passages for the flow of air. This perhaps is best shown in Fig. 5 of the drawing. Here it is seen that air entering past curved entrance lips 47 goes around the cylindrical curved side baffles 43 and up through a center passage 24 to the plenum boxes 44. Inasmuch as two cylinders are shown and the device indicated in Fig. 8 is half of a normal device, the two plenum boxes of opposed symmetrical cooling sections are attached together by appropriate means such as bolts 49. Each of the plenum boxes 44 is connected to a ducting tube 48 terminating near an exhaust jet 30, which will be more fully explained later.

In the engine section, immediately above the cylinder walls 11, there are positioned combustion chambers 13 having separate cooling fins 14. For convenience, only one of these combustion chambers 13 is described. Each combustion chamber is separately bafiled and has a separate inlet created by a curved entrance of a baflie flange 62, leading to. a side wall or area casing 63 surrounding the fins 14 leading to a bottom plenum chamber 54. It is to be understood that the flow of air through this section around the cylinder combustion chamber is guided by the cylinder fins 14 as Well as the particular baffie structure illustrated leading to the plenum chamber 54.

In this plenum chamber 54, the air from around the combustion chamber is admixed with the air passing around a head portion 15 of the engine between various head fins 16. It is guided in this passage by means of curved opening flanges 66 leading to a head fin bafile 65. The lower plenum chamber 54 is attached to the wall 63 as well as a primary suction chamber 53 of the entire bafile structure by means of appropriate bolts 55. The chamber 54- has a common wall 58 with the adjacent plenum chamber and is provided with upper openings 57 for the passage of valve push rods 21 leading from the crankcase 22 of the entire engine, to the outermost fin of the engine head casting. The end portion of the plenum chamber 54 leads into an end port 56 which, in turn, passes to the area enclosed by the primary suction chamber 53 leading up and around the exhaust jet nozzle 39. This nozzle consists of an exhaust jet flange 31 leading to a curved exhaust body 32 terminating in a substantially cylindrical opening 33. This exhaust nozzle assembly and gaskets are held in place against the head portion 15 of the engine by appropriate bolts 34.

Positioned immediately below the chamber Sd is a fin type oil cooler 71 having open ends 73 leading to a cooling passage 72, which in turn, terminate in a tube 74 communicating with the interior of the chamber 53, as indicated in Figs. 1, 2 and 11.

The exhaust nozzle 30 is positioned internally and substantially concentric with a cylindrical mixer section 37 which, in turn, leads to a conical shaped diffuser section 70 as shown in Fig. 11 of the drawings. Appropriate strap bands 3% attach to the mixer section 37 and the outlet dil of the primary suction chamber 53. As is best shown in Fig. 6 of the drawings, the cylindrical mixer section 37 is positioned so that air coming through the tube 4% is diverted by means of a curved baflie 50 so as to enter the chamber 53 immediately adjacent to the outlet of the nozzle 30. The air coming through the plenum chamber from the plenum chamber 54 is admixed in the chamber 53 with air from the tube 48 and the tube 7- The volumes of each of the several streams of cooling air indicated in the vicinity of the exit exhaust nozzle 3% as well as the velocities of these streams are critical. The dimensions of the cylindrical mixer section 37 are also critical. Air from this mixer section is preferably conveyed to the difliuser section 70 as illustrated in Fig. 11.

in order for there to be optimum engine performance, it is usually desired that temperatures of difierent parts of the engine proper and the lubrication oil employed be at difierent levels. Thus, for example, in the engine illustrated in Figs. 1 through 8 of the drawings, optimum performance is obtained with the cylinder barrel temperature less than 150 C. and with the temperature of the head at about 200-230 C. or just below the autoignition point of the gas-fuel mixture used with the engine. These temperatures can be easily achieved in accordance with the present invention by regulating the quantity of cooling air drawn past each of the sections of the engine through the channels created by the cooling fins surroundi 2 these sections, These channels in effect serve as valves limiting or governing the quantities of air used for cooling. If desired, restricted openings leading to the channels can be used to achieve the same purpose. Obviousiy, the quantity of air drawn through them will vary depending upon the suction created by the exhaust jet pump utilized.

in designing a jet cooling system of the type herein described, it is best to first determine the minimum size of the exhaust nozzle that can be used without adversely affecting the performance of the engine. Small nozzle sizes are desired in order to obtain highest possible velocities through the nozzle. Too small a nozzle, however, will cause such a high exhaust back pressure that engine performance 'is adversely afiected. Frequently, this back pressure is as high as 40 of Water in automotive practice. A particularly satisfactory jet cooling system of the type shown in the initial figures of the draw ing has been created by using a back pressure on the exhaust nozzle of about 20" of water. When this engine is operating at from about 1,000 to about 5,000 R. P. M., the exhaust velocity varies from about 415 to about 1840 feet per second. With such velocities a diameter exhaust jet of the type shown in Fig. 7 is disposed in a 2 /2" diameter mixing section, giving a ratio of the area of the mixing section to the area of the jet of approximately 10:1. With this ratio between the areas, satisfactory cooling of the type desired is created. For any given application, it is best to experimentally determine the precise area of the mixing section surrounding the exhaust jet for optimum pumping of the cooling air even though the ratio of the area of this section to the area of the jet is normally within 25% of the 10:1 ratio given above.

When using comparatively short mixing tubes, more efiicient mixing of the exhaust gases and cooling air can be obtained by using a cruciform type of exhaust nozzle opening 33 as indicated in Fig. 9, than can be obtained by using a circular exhaust nozzle opening as shown in Fig. 7. The shape of such nozzles bears a relationship to the amount of gas pulled around the cooling fins. In general, the greater the circumference of the exhaust jet area, the more eli'lcient the pumping action obtained when used in conjunction with short mixing tubes.

it is possible within the scope of the present invention to increase the efficiency of the pumping action attained by approximately 25% by utilizing a comparatively straight mixing section of substantially uniform crosssectional area whose length is preferably within the range of from 4 to 7 times its diameter. In all cases, this length is measured from the exhaust nozzle itself. This mixing section cannot be bent beyond about a 15 turn without materially affecting the results obtained.

Approximately another 25 increase in pumping efi'iciency results from the connection of a diffusing section onto a mixing section of the type described above. A diffusing section to be efiective must be conically shaped with its walls forming an angle of about 10 with one another. It is to be understood this angle may be varied slightly without noticeable eflect. Also, a diifusing section can be curved around corners and the like, Without material loss in efficiency, provided the curves employed are smooth and are not sharp in character. In general, the longer the difiusing section employed, the more eflicient is the pumping action obtained. For practical reasons, it is preferred to have such a section no longer than about 10 times the diameter of the mixing section with which it is used. The increase in pumping efiiciency obtained with longer lengths than this is normally considered too small to justify the cost involved in extending the diffusing section.

With the specific construction illustrated in Fig. 11 of the drawings, the difiiuser section is connected to a second pumping stage 89 consisting of a jet nozzle 81 formed from the end of the diffuser section 70 around which there is disposed an inlet chamber 79 having an air inlet opening 85. This nozzle 81 leads to a straight mixing section 82 and this in turn leads to a diffusing section 83. Around the sections 82 and 83, there is disposed a quantity of an appropriate insulating material -84, such as for example, glass wool. If desired, perforations can be provided between the insulating material 84 and these sections 82 and 83 in order to obtain a sound mufiiing action. Similar perforations can be provided for the same purpose within the jet nozzle 81, and, further, a limited amount of packing can be placed around this nozzle, although these expedients are not usually considered necessary and/or advisable. Surprisingly, if the inlet chamber 79 is made large enough, a substantial muiliing action can be obtained from it when the inlet opening 35 is provided with a cap 86. If desired, the second pumping stage 89 can be used by connecting this inlet opening 85 to any volume of gas it is desired to exhaust, such as for example, an enclosed compartment of a car. A plurality of separate pumping stages 01 this type can be employed, if desired, in order to exhaust separate cooling air streams, although this is not preferred normally because of size limitations. Each pumping stage of a series of pumping stages must inherently be longer than the preceding stages in order for there to be eflective pumping action.

For specific installations, other than the one illustrated, it is frequently desired to use a construction such as one shown diagrammatically in Fig. 10, wherein a plurality of concentric cylinders distribute the exhaust gases over a relatively large area so as to obtain efiicient mixing of the cooling air and exhaust gases and so as to obtain efiicient pumping action.

Those skilled in the art will realize that the present invention is of comparatively broad scope and represents a serious effort to selectively cool parts of an engine to a predetermined extent by means of air streams drawn with jet pumping action created by means of the exhaust of the engine.

Those skilled in the art will realize that the herein described invention is capable of wide modifications within the scope of the present disclosure. Such modifications are to be considered part of the present inventive concept insofar as they are defined in the appended claims and insofar as they are within the ability of those skilled in the art.

1 claim as my invention:

1. A new and improved device for cooling engines, which comprises: an exhaust nozzle; means for attaching said exhaust nozzle to an exhaust gas outlet port of an engine; a plurality of bafiie means adapted to surround separate functional parts of said engine and define a plurality of cooling air passages therewith, said air passages being of different areas, whereby said parts of said engine may be cooled to varying extents; exhaust casing means surrounding said exhaust nozzle and defining therewith 6 a substantially straight mixing section of substantially uniform cross-sectional area forming part of an exhaust pump; passage means connecting said cooling air passages with said exhaust casing means, whereby when exhaust gases are passed through said nozzle, said exhaust gases cause air flow through said air passages; a diffusing section attached to said exhaust casing means at a point thereof remote from said exhaust nozzle, said diffusing section beingsubstantially conical; a jet nozzle attached to said diffusing section at a point remote from said exhaust casing means; and an inlet chamber disposed around said jet nozzle and having an inlet opening surrounding the terminal extremity of said jet nozzle.

2. A device as defined in claim 1, wherein said inlet opening and said jet nozzle empty into a second mixing section, said mixing section being substantially straight and of substantially uniform cross-sectional area.

3. A device as defined in claim 2, wherein a difiusing cone is attached to said second mixing section at a point thereof remote from said jet nozzle.

4. A device as defined in claim 1, wherein a plurality of cylindrical baflie means are placed around said exhaust nozzle.

References Cited in the file of this patent UNITED STATES PATENTS 763,949 Anderson July 5, 1904 1,816,161 Strauss July 28, 1931 2,288,017 Neuland June 30, 1942 2,410,856 Koppen Nov. 12, 1946 2,583,651 Horning Ian. 29, 1952 FOREIGN PATENTS 14,483 Great Britain Nov. 20, 1913 40,112 Sweden Feb. 2, 1916 142,308 Great Britain Apr. 29, 1920 363,057 Italy Sept. 16, 1938 980,900 France May 18, 1951 

